Brie Larson reveals the hardest part about becoming suddenly very famous

Brie Larson's stardom blew up after she starred in "Room" in 2015, for which she won an Oscar.

She says the hardest part about being famous is using her voice.

"I just don't really understand why anybody would care what I have to say," she says.

Larson is using her platform for important social causes.

Fame certainly has its perks. You get a lot of things for free. You pretty much never have to wait in line for anything. Making money becomes much easier. But there are some negatives. The most obvious is the loss of anonymity.

Brie Larson admits that that's the biggest thing she's tried to wrap her head around since becoming a bone fide celebrity after winning the Oscar for best actress for 2015's "Room."

"I don't think I'll ever be able to grasp this — I just don't really understand why anybody would care what I have to say," Larson told Business Insider while doing press for her new movie "Free Fire" (opening Friday). "I'm just a person figuring stuff out. That's the thing I trip out on all the time when I do days and days of press and you're like, 'Who cares what I think?'"

But people care very much. And Larson has turned that into a positive force. She's used her platform to be vocal about issues that are important to her like support for sexual-assault victims and giving women and minorities stronger voices in Hollywood.

Her visibility will only increase in the coming years as we near the 2019 release of Marvel Studios' first movie with a female lead, "Captain Marvel." Larson will be our Captain Marvel.

But there is one thing from her old life she can still do.

"One of my favorite things in the world is just to people-watch and to listen," Larson said.

There are moments when she can go out in public and not be recognized.

"And I'm very paranoid about my privacy so I would be the first to tell you if it's all gone. It's not. I'm grateful for that," Larson said.